A waste water pump has as a rule only one heat source from which heat, generated during operation of the pump, must be carried off in order not to damage the heat source or having the heat source to be turned off by means of conventional protection equipment due to a too high temperature in the pump. This heat source is constituted by the electrical motor of the pump, which electrical motor is arranged in the motor compartment of the drive unit. The stator of the electrical motor is pressed into the motor casing/stator housing of the pump and the heat is carried off to the surrounding media. The surrounding media is constituted by a liquid if the pump is immersed/submerged and is alternatively constituted by a gas if the pump is dry installed. In the latter case the heat transport to the surrounding media is insufficient and is reinforced either by means of external air cooling using fans or by means of heat transport via the motor casing/stator housing to the heat sink of the pump, which in its turn is cool down by the liquid that is draw into and pump out from the pump.
Usually the electrical equipment is arranged in a coupling compartment that is located on the opposite side of the motor compartment in relation to the heat sink, i.e. in the top of the pump, and this electrical equipment has in previously occurring pumps not required dedicated cooling. In the most elementary design the electrical equipment is constituted by a connection block intended to connect the incoming electric cable and the internal cabling.
However, the future pumps will more often comprise an internal power supply component arranged in said coupling compartment, and in contrast to other electric equipment such power supply components require dedicated cooling in order not to be damaged and in order not to have the safety equipment turning off the pump due to a too high temperature at the power supply component. Due to the fact that the coupling compartment is located un top of the motor compartment in relation to the lower heat sink, the heat in the coupling compartment has to exceed the heat in the motor compartment in order to have the heat carried off from the coupling compartment past the intermediate motor compartment and to the lower heat sink. However, the electric motor generate much more heat than the power supply component, and the coupling compartment and the power supply component are heated by the motor instead of being cooled off in the desired way, which has a negative effect on the power supply component and lead to undesired safety stop of the pump.